1. Field of the Invention
The present invention relates to a content sales price accounting system and a content sales price accounting method in a content distribution system for selling a content by distributing an encrypted content and supplying a person desiring to purchase the content with a key for decrypting the encrypted content.
2. Description of the Related Art
With the widespread use of CD-ROM drives, a content such as a film, musical work, computer program, database, etc., in the form of software and defined as digital data is frequently distributed through a CD-ROM medium. The CD-ROM medium can be manufactured at low cost and has a large capacity exceeding 500 MB. In addition, CD-ROM drives are decreasing in price and increasing in speed. Further, the CD-ROM is comparatively lightweight and thin for its storage capacity and, therefore, can be distributed by various methods, including being interposed in a magazine for distribution or other uses.
The content of the CD-ROM is stored as digital data; therefore the content can be illegally copied and installed (the term "install" herein connotes an introduction of the content into a disk device of a personal computer). Accordingly, when distributing the content of the CD-ROM, illegal copying and installation must be prevented.
Accordingly, the following has hitherto been practiced. In distributing the content by CD-ROM, several types of trial versions of the content and an encrypted real content are recorded on the CD-ROM, and thus distributed. Only a user paying a using charge (which is a one-time payment) for the content is supplied with a key for decrypting the encrypted real content, permitting the user to use the real content. For the purpose of explanation, the phrase "supplying the key in exchange for the payment of the using charge for the content" is expressed in terms such as "selling the content", and the phrase "the using charge for the content" is termed a "sales price of the content".
In the conventional content distribution system described above, the sales price of the content is fixed at all times.
However, consider the case of, e.g., contents (such as contents for which timeliness of information is important such as in text data of a magazine or news paper, and contents with a high seasonality, such as in musical data of a Christmas song, video data of a Christmas movie and image data of a New Year's card) having an automatically limited period for which the contents are allowed to be mass-sold at considerably high prices. In such a case, an operator of the content distribution system or a content provider is inclined to desire a sales price as high as possible within the sales period thereof. Similarly, for some contents sales contracts previously prescribe limits of sales periods for which the operator of the content distribution system are allowed to sell the contents. I these cases also, the operator of the content distribution system is inclined to want the sales prices to be as possible within the permitted sale periods. Further, for a content for which that a software upgrade is scheduled at an interval of a given period, as in the case of a computer program, the sales quantity of the content may decrease drastically just before the upgrade becomes available. Hence, the operator of the content distribution system or the content provider tends to reduce the fall-off in sales quantity as much as possible by reducing the sales price.